Interferons are glycoproteins that produce in cell cultures a reduction in virus multiplication. This antiviral activity makes them promising agents in the treatment of viral diseases in man. Interferons are also considered as possible anti-cancer agents. Assays of interferons were done, until now, by measuring the reduction of the growth of a certain virus, in cells exposed to interferon. These assays are time-consuming and variable because of the need for virus infection.
Assays for interferon previously described are based on a pretreatment of cells with interferon for 10-20 hours, followed by infection with a test virus for at least 8-10 hours, and usually 24-48 hours. A viral product or a cytopathic effect is then measured. The need to infect the cells introduces an additional variable and requires additional controls in the test.